So 150-200 times 2-4 Mbps is 300-800Mbps for the whole country.

There are about 5 million people in New Zealand. About 13 percent are rural. Let's say 30% of those are in areas where this would be useful, or about 4%. 200,000 people, and about half are the age and temperament to have a cellphone. Let's say they're using this data 1% of the time. That's 1000 people at a time, on average. So the useful data rate per active person is about 800kbps. That's not great, but still usable even for 240-360p video streaming, music streaming, navigation, normal web stuff. About 2.5 Gigabytes per month per 100,000 subscribers (although due to time of day, etc, that's probably more like a usable 1-1.5GB per month). For casual users with wifi at home, that's not that bad. I think my wife uses about that much or less.

2-4mbps is better than 0 even if it is divided by all users in that area.

Especially considering that in a lot of areas this will open up coverage to, you could be the only user relying on it anyway.

I think pricing will determine how useful it is. If you take the 2% of the population in the 50% of the country that doesn't have terrestrial coverage then the bandwidth isn't really that bad - it's the same or better than other options in a comparable footprint or reasonable cost with the bonus it'd be on the same device you normally carry with you which auto switches back to high speed when you're in town.